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UCC5880-Q1: Reading register always get the same command back

Phoenix Yin
Intellectual 295 points
Part Number: UCC5880-Q1

For example, when trying to read CFG3 register after power on, I sent 0x0102, then 0x0542, on the SO line, I could see the response is 0x0102. The ucc5880 always returns the command that it received. 

It seems the chip is in a special state but could not find the explanation in the datasheet. Any idea?

This is the response when sending NOP to read CFG3. You can see that send NOP out and get the command 0x0102 back.

  • +1
    TI__Expert 5921 points

    Hello Phoenix,

    Thanks for reaching out.

    The behaviour you describe matches the design to allow Daisy Chain SPI mode.

    This would mean multiple commands are getting sent to the SDI pin while the nCS pin stays low. The nCS pin should be asserted for each command, and pull high again before the next command. If the nCS pin stays low through multiple commands the gate driver will act a sa shift register, matching what you describe.

    Could you probe the same signal again, but this time also showing the nCS pin?

    Thanks,

    Daniel

  • 0 in reply to Daniel Norwood
    Intellectual 295 points

    Hi Daniel,

    It does solve the problem, silly me '_'

    Thanks